The output of a gas turbine can be adjusted by altering the turbine inlet temperature, the compressor inlet mass flow, or both parameters. For adjusting the compressor inlet mass flow, for example the inlet geometry of the compressor can be altered via a variable inlet guide vane cascade.
The level of the turbine inlet temperature essentially determines the service life consumption or the length of the inspection interval of the gas turbine.
The efficiency of the gas turbine is essentially determined by the pressure ratio which with constant turbine inlet temperature progresses proportionally to the compressor inlet volume.
The output of a gas turbine is essentially determined by the level of the turbine inlet temperature. The gas turbine exhaust temperature is directly proportional to the level of the turbine inlet temperature and inversely proportional to the pressure ratio of the gas turbine.
The efficiency of a combined gas and steam turbine power plant, that is to say of a so-called combined cycle power plant, is dependent upon the level of the gas turbine exhaust temperature and upon the gas turbine efficiency. From this, it follows that the overall efficiency and the output of a combined cycle power plant is essentially dependent upon the gas turbine inlet temperature.
Nowadays, gas turbines are controlled so that a prespecified rating of gas turbine inlet or exhaust temperature/compressor inlet guide vane cascade position, or the variation of the temperatures for predetermined compressor inlet guide vane cascade positions, is associated with each load.
Minimizing the electricity production costs in the sense of a flexible adaptation of gas turbine inlet temperature and/or of the position of the compressor inlet guide vane cascade is possible only in the case of a new commissioning during which the corresponding rating or variation of the gas turbine inlet temperature or gas turbine exhaust temperature and of the position of the compressor inlet guide vane cascade is established for achieving specific maximum or minimum load values or as a function of the load. If, for example in the case of an increase of the fuel price, the wish should be to reduce the efficiency with simultaneous extension of the service life and consequently of the maintenance interval with constant electric power output, a new commissioning of the gas turbine would be necessary for this.